The present invention relates to a light controller for adjusting an amount of shooting light for a still camera, a video camera, and so on. In particular, the present invention relates to a blade and a driver for driving the blade used for a light controller disposed in a shooting optical path for controlling an amount of light passing therethrough to a proper amount of shooting light with multiple blades, a shutter device for shutting off light passing through a shooting optical path, and a light controller for controlling an amount of shooting light.
Generally, a light controller has multiple blades in an optical path and controls an amount of light reaching an image pickup device such as a photoelectric transformer and a light-sensitive film by opening or closing the blades. The control of an amount of light may be implemented with diaphragms for adjusting an amount of light reaching the image pickup device to a proper amount of light exposure or shutter blades for shutting light reaching the image pickup device off. Alternatively, the control of an amount of light may be implemented with a dual-purpose diaphragm and shutter device for controlling the opening and closing of blades at predetermined positions and then moving the blades to the closed position, so that the adjustment of an amount of light exposure and shutter operation can be performed simultaneously. These blades include multiple, for example, a pair of blades attached to a substrate having an optical path opening, and a transmitting arm at an axis of rotation of a drive motor is associated with the blades, whereby the optical axis opening can be adjusted in an arbitrary manner.
A conventional device is disclosed in Japanese Patent Publication (Kokai) No. 11-194382. Japanese Patent Publication (Kokai) No. 11-194382 discloses a structure including a substrate having an optical path opening in an shooting optical path and a pair of blades attached to a substrate for opening and closing the optical path opening, so that the opening/closing of the pair of blades can be driven by a drive motor. The pair of blades has tips facing toward the optical path opening, base ends slidably supported by the substrate, and slits in the pair of blades to which associating pins of driving arms attached at an axis of rotation of the drive motor fit, so that the blades can be moved in opposite directions. The driving arms and slits are conventionally configured such that the drive motor and the pair of blades can move at an equal speed. Accordingly, the size of the optical path opening can be adjusted or the opening can be closed by synchronously moving the blades in opposite directions by an equal amount with reference to the center of the optical path opening.
The structure for opening and closing the blades in the conventional device will be described with reference to FIGS. 6A-6C to 8A-8C. FIGS. 6A to 6C show a case that an optical path opening X5 is closed and opened by a first blade X1 and second blade X2. The blades are guided and supported so as to move in horizontally opposite directions with respect to a substrate (not shown). The first blade X1 has an arc-shaped opening edge, and the second blade X2 has a semicircular-cl)t opening edge. The first blade X1 and second blade X2 have slits X3 and X4, respectively, and pins of transmitting arms mounted at an axis of rotation of a driver are configured to associate thereto. The slits X3 and X4 tilt symmetrically at an equal angle such that rotational forces of the transmitting pins can be uniformly transmitted to the first blade X1 and second blade X2.
With this construction, the half-open state shown in FIG. 6B is obtained when the first blade X1 is moved to the left side in FIG. 6A and the second blade X2 is moved to the right side in FIG. 6A from the entirely open state in FIG. 6A. The entirely closed state shown in FIG. 6C is obtained when the first blade X1 and second blade X2 are moved further. The first blade X1 has, at the center thereof, a larger opening than the optical path opening X5 and further has an opening/closing portion X6 at the right edge for covering the optical path opening X5. Thus, the first blade X1 at the state in FIG. 6A completely opens the optical path opening X5 (entirely open state), and the blade is at an open position. The right side of the optical path opening X5 is covered (half-open state) in the state in FIG. 6B, and the blade is positioned at the middle position. The optical path opening X5 is completely covered (entirely closed state) in the state in FIG. 6C, and the blade is at a closed position in this state.
On the other hand, as shown in FIG. 6C, the second blade X2 has a semicircular right edge and completely opens the optical path opening X5 at the open state in FIG. 6A, covers the left edge of the optical path opening X5 at the middle position in FIG. 6B, and overlaps with the first blade X1 by shown Delta 1 at the closed position in FIG. 6C. There, the entire length (L3) of the two first and second blades are maximum at the entirely open state where the blades are positioned at the open positions in FIG. 6A, and the substrate supporting these blades is longer than the length L3. Next, the first and second blades form an aperture at the center by covering a part of the optical path opening X5 at the middle position in FIG. 6B, and the aperture has large and small similar apertures about the optical axis of the optical path opening.
Thus, the first and second blades always form an aperture about the optical axis by being moved and displaced by an equal amount from the entirely open state. At the entirely closed positions in FIG. 6C, the first and second blades overlap with each other only by shown Delta 1. The overlapping keeps an amount of overlapping enough for preventing light from entering from a gap caused by a deformation or vibrations of the blades. The amount of overlapping between the blades at the entirely closed state is influenced by a rebound caused when the blades are moved fast and then stopped at the closed positions.
In particular, in a fast diaphragm device or fast shutter device, for example, is attempted, the rebounds of the blades moving fast may allow unnecessary light to enter. Therefore, the amount of overlapping must be increased. If an amount of overlapping Delta 2 (Delta 2>Delta 1) is increased as shown in FIG. 7C, a gap G1 occurs between the edge of the first blade X1 and the edge of the optical path opening. The gap G1 is increased as the amount of overlapping Delta 2 increases while the blades having a reduced size cause a large gap by the reduced amount.
FIGS. 8A to 8C show a case that the length of the blades is increased by L4 from the one shown in FIGS. 6A to 7C. No gap occurs in processes that the blades move from the entirely open state in FIG. 8A to the aperture position in FIG. 8B and to the closed position in FIG. 8C. However, the total length of the blades increases (L3+L4), and the device is larger than those in FIGS. 6A to 7C.
In this way, in a conventional device, two blades facing toward an optical path opening move at an equal speed from the entirely open positions to the aperture positions and then to the entirely closed positions about the optical axis. Therefore, the amount of overlapping must be increased in order to prevent light from entering due to rebounds of the blades at closed position when the blades are moved fast particularly in a shutter device or dual-purpose diaphragm and shutter device.
As described above, a conventional device having multiple blades in the optical path opening moves and displaces the multiple blades at an equal speed by an equal amount in order to control an amount of light passing through the optical path opening or shutting passing light off. Therefore, the amount of overlapping of the blades at the closed positions must be increased in a shutter device or dual-purpose diaphragm and shutter device that opens and closes the blades fast in order to prevent an effect of a rebound caused when the blades are closed.
As a result, the size of the device is increased as the amount of overlapping between the blades increases. Furthermore, the load on the driver for driving the blades is also large, which disadvantageously increases the size of the entire device.
Accordingly, it is an object of the present invention to provide a small and inexpensive light controller having a simple structure including multiple blades facing an optical path opening and moving at different speeds between the entirely open position and the entirely closed position; so that the blades can be opened and closed fast without particularly increasing an amount of overlapping between the blades, causing a gap between the blades at entirely closed state and the optical path opening, and causing a gap between the blades due to a rebound caused when the blades stop.
Further objects and advantages of the invention will be apparent from the following description of the invention.